In a saucepan, sauté onion, carrot, celery and garlic in oil, until tender. Stir in chicken broth, rice, basil, & pepper. Bring to a boil. Reduce heat, cover & simmer for 15 minutes, until rice is tender. In small bowl, combine flour and milk until smooth, stir into soup. Bring to a boil, cook and stir for 2 minutes. (or until thickened) Stir in chicken; heat through serve.